Blender Scale Issues with MakeHuman and Mixamo Fuse
Without seeing a ~.blend file containing both imported images, this is a bit of shot in the dark, but the first thing I would try is to open the file, select the model that is in the smaller scale in object mode, then switch to edit mode, and scale the model up until the proportions approximate those of the first model imported. Then switch back to object mode, and apply the scale of the object using CTRL - A. 

Of course you could use the same technique in the reverse direction to scale the larger object down to the smaller one.